The clash broke out at around 10:00 am (0300 GMT) in a district bordering Myanmar in northern Chiang Mai province when 10 people refused official calls to stop after crossing the frontier, according to border patrol police.
"Five hill tribe people were shot dead during the fighting and we seized six bags carrying a total of 420,000 tablets of methamphetamine," a local border patrol police officer, who did not want to be named, told AFP by telephone.
"Hill tribe people" is the term used in Thailand to describe the various indigenous tribes living in the northern and western parts of the country.
There were no casualties among security forces, the border patrol officer added. Police said the other five indigenous people escaped custody.
Deputy national police chiefPongsapatPongcharoen said the drugs seized had a street value of 4.2 million baht ($128,000).
Clashes between security forces and drug traffickers are fairly common in the kingdom's remote border regions.
Thailand has seen a marked increase in seizures of methamphetamine, which is relatively cheap and easy to make and is often smuggled from Myanmar by armed rebel groups using profits from narcotics to fund their operations.
© 1994-2014 Agence France-Presse