Marcus Evans, from Weston-super-Mare, and his friend were attacked with a sickle-shaped knife while drinking and playing music in the early hours of Saturday in Kanchanaburi, central Thailand, according to local media.
Mr Evans’s partner paid tribute to him on social media, the Daily Mirror reported.
She posted a picture of the couple together, saying: “And just like that another person I loved dearly…. Gone xxx.”
The second victim, named as Kevin Dagnan, from Nuneaton, in media reports was taken to hospital after the attack.
A friend, Adria Licci, 59, from Italy, who also lived in the resort, told media: “They also knew the attacker and they had drinks with him before and had given him cigarettes. They used to joke with him a lot.”
She said she had heard a loud argument around 3am before seeing Mr Evans lying on the ground seriously injured.
Officers from the local Mueang Police found a sickle and a pair of shoes at the scene.
They later arrested a 23-year-old local man. Reports on Saturday suggested he had been attacked by angry residents who suspected him of being the perpetrator.
Officers believe that the two victims had been playing music and drinking before being attacked after a row escalated.
A Foreign Office spokesperson said: “We are in contact with the Royal Thai Police following the death of one British man and the hospitalisation of another in Thailand and are ready to provide consular support.”
The alleged attacks took place outside a rented room in Mueang, Kanchanaburi.
A neighbour told police that he heard a loud noise outside while he was asleep and rose to find the two Brits.
The arrested man lived nearby and had a history of mental health problems, according to police.
Police Colonel Somkiart Chomchai said a team of police, including forensic officers, were dispatched to the scene to collect evidence.