Java Sea: Royal Thai Navy
The Road to Koh Chang, Part Two
by Mike Bennighof, Ph.D.
June 2024

Our story began in Part One.

The central government at Vichy approved the plan for a naval attack against Thailand on 13 January 1941. The Indochina squadron was to seek out and destroy Thai naval forces and shell targets along the Thai coast, all in the interest of drawing attention away from the land front.

For the attack, Capt. Régis Bérenger took the risk of sending his very slow sloops and gunboats ahead of his light cruiser Lamotte-Picquet; if spotted, they might not be taken as an attacking fleet and thus avoid provoking an enemy response. He remained in Saigon to collect reports from aerial reconnaissance and adjust his plans until the last moment. Before leaving Saigon, Lamotte-Picquet flew off her pair of Loire L130 seaplanes, to join the small half-squadron based at Ream and remove the fire hazard before battle.

The Thai fleet gathered at Koh Chang (“Elephant Island”) roadstead normally included at least one of the Thonburi-class armored coast defense ships, plus torpedo boats and other vessels. Either of the two biggest ships was probably a match for Lamotte-Picquet in a firefight, and they were often both present. The Thais also had a pair of armored gunboats with 152mm guns, but these usually remained at Sattahip, the naval base just south of the Thai capital, Bangkok.

The coast-defense ship Thonburi.

French seaplanes noted one coast-defense ship and a torpedo boat at Koh Chang, and one of the armored gunboats and four more torpedo boats at Sattahip. The second coast-defense ship was not spotted. Koh Chang was closer, with fewer of the torpedo boats (potentially deadly to the slow-moving French sloops), and was known to have no harbor defenses. Bérenger met up with his sloops and gunboats on 15 January and steamed for Koh Chang the following night, timing his arrival for a dawn attack on the 17th.

The French arrived exactly as planned. Lamotte-Picquet entered the anchorage through its widest entrance, to the east. The modern sloops Amiral Charner and Dumont d’Urville entered the roadstead through the southern gateway while the ancient gunboats Tahure and Marne sealed off the western exit. They arrived with the sunrise, along with perfect weather and calm seas. The Thais actually had two torpedo boats present, not just the one reported by aerial reconnaissance.

Bérenger achieved complete surprise, catching the Thai crews still asleep, but two French seaplane pilots threw away his advantage with a rather hapless air attack on the small Thai fleet. The now-alerted Thais actually opened fire first, but failed to score any hits. Fearing torpedo attack, Bérenger’s cruiser concentrated her fire on the two torpedo boats, sinking both, and also fortuitously destroying a shore-based observation post that her spotters mistook for a third torpedo boat. The building also housed a radio transmitter, and its loss slowed reporting of the French attack to the Thai naval command and the dispatch of aircraft.

Crewmen from the transport Chang fight Thonburi’s fires; note the short hose.

The coast-defense ship Thonburi opened fire on Lamotte-Picquet with her forward 200mm (7.9-inch) guns, firing rapidly but obtaining no hits – both of the Thai ship’s turrets only rotated slowly and the French cruiser’s bridge officers speculated that they were being trained by hand; Thai accounts claim that the turrets were damaged early in the fight. The cruiser shifted her fire to Thonburi, and the first salvo killed the Thai ship’s commander, Capt. Luang Phrom Virapan. In the confusion that followed, the French sloops also opened fire on Thonburi and executive officer Lt. Thongyu Sawangnet ordered the Thai ship to switch targets to the sloop Amiral Charner, leaving Lamotte-Picquet undisturbed. That allowed the French cruiser to hit the Thai ship repeatedly, putting her aft turret out of action and starting at least three fires. Thai accounts also claim that a seaplane hit Thonburi with a bomb, but this is not mentioned in Bérenger’s report.

Sawangnet ordered the magazines flooded, but the valves failed to work properly (or were not operated properly) and much of the ship flooded as well, causing a heavy list. Thonburi still had limited maneuverability; though trapped in the engine room by fires the black gang continued at their posts until all eight were overcome by smoke inhalation and died. The Thai vessel veered into shallow water where the cruiser could not follow, listing badly and finally running aground on a sandbar.

After about two hours of action, Bérenger ordered his ships to break off and return home before Thai aircraft could intervene. Thai planes attacked within minutes of his order, scoring one hit on Lamotte-Picquet which failed to explode. The French escaped with no serious damage to any of their ships, and eleven sailors killed.

The Thais lost 36 killed, including their commander, and all of the ships involved. Nonetheless they claimed victory, on the basis of the French having withdrawn from the area. The transport Chang came alongside Thonburi soon after the French departed and tried to help fight the fires with her pumps, but she lacked hoses long enough to reach the fires. She instead attempted to tow the still-burning ship back to Sattahip, but when this didn’t work either, Sawangnet ran his ship aground on a sandbar to concentrate on putting out the fires. The transport took off the coast-defense ship’s wounded, and Sawangnet ordered his men to abandon ship.

Thonburi burns while her crew mills about in confusion.

More sailors and local residents swarmed onto the sandbar to try to extinguish the flames, but this also failed and late in the afternoon Thonburi slipped off the sandbar and capsized, sinking with her keel and starboard rudder still visible above the water. The Thais would later raise the badly-damaged hulk and employ her as a stationary training ship. She was scrapped in 1959 with her forward turret and bridge preserved ashore as a memorial at the Royal Thai Naval Academy in Samut Prakan.

The Thais also dispatched their other coast-defense ship, Sri Ayudhya, and the torpedo boat Trad that had been lurking just north of the anchorage (and never detected by the French). The French had departed by the time they arrived on the scene and they returned to Sattahip.

The battle had an immediate impact on the overall war situation, though probably not what either side had expected. These Japanese quickly stepped in to impose a mediated settlement on the warring parties. Thailand would receive the disputed border territories, with a cease-fire taking effect on 28 January and a permanent peace in May 1941. Thailand would be forced to cough up the provinces again at the end of the war.

Marshal Phibul had a victory memorial erected in Bangkok. The French Navy has never memorialized its victory at Koh Chang, as it occurred under the traitorous Vichy regime; a few plaques and museum displays are the only remembrance.

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Mike Bennighof is president of Avalanche Press and holds a doctorate in history from Emory University. A Fulbright Scholar and NASA Journalist in Space finalist, he has published a great many books, games and articles on historical subjects; people are saying that some of them are actually good. He lives in Birmingham, Alabama with his wife, three children, and new puppy. He misses his lizard-hunting Iron Dog, Leopold.

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