Two female Russian tourists were shot dead on Saturday while they were relaxing on the beach in the popular Thai seaside town of Pattaya, police said.
Tatiana Tsimfer, 30, and Liubov Svirkova, 25, were found dead in their deckchairs on Jomtien beach, Pattaya, some 150 kilometres southeast of Bangkok, they said.
A nearby hotel guard told police he heard several gunshots and saw a Thai man speeding away on a motorcycle after the shots.
"At the moment, we don't know why they were shot," Major Sretha Maklon of Pattaya police told AFP on the telephone. The women arrived in Thailand on February 16 as part of a group tour.
Pattaya is one of Thailand's popular beach resorts and is also known for its thriving nightlife.
Despite its reputation as a holiday paradise, Thailand has seen a series of gruesome murders of tourists in recent years.
In Kanchanaburi, 100 kilometres west of Bangkok, a 26-year-old female Australian tourist was killed in a drive-by shooting last year. A young British couple were gunned down there in 2004 and a French tourist was shot dead in 2003.
On New Year's Day in 2006, a 21-year-old British female tourist was raped and murdered on the southeastern resort island of Samui.