Thai police are trying to establish a motive for the killing of two Russian women who were shot dead in their deckchairs on a beach in Pattaya.
The tourists from Kemerovo in Siberia were killed early on Saturday. Police say each had been shot several times.
Pattaya, some 150km (93 miles) south-east of Bangkok, is famous for its beaches and buzzing nightlife.
Police say the women's bodies did not show signs of a struggle and personal belongings remained at the scene.
A witness said he saw a young man running away from Jomtien Beach and speeding off on a motorcycle immediately after the shooting.
The women were named as Tatyana Tsimfer, 30, and Liubov Svirkova, 25. Both worked for telecoms firms in Kemerovo, Russian media report.
The Thai newspaper The Nation says a security video showed a tall man parking a motorcycle by the beach, running up to the women and shooting them before fleeing.
"From the gunman's dress - jeans and boots - we suspect he is a member of a Pattaya teenage gang," said a police officer, Lt Gen Asawin Kwanmuang.
Police have offered a 100,000-baht ($3,000; £1,525) reward for information leading to the arrest of the killer.