The explosions took place thirty minutes apart in the bar district of the popular beach town of Hua Hin late Thursday night, the latest incident to threaten Thailand's reputation as a holidaymaker's paradise.
Small blasts are common in Thailand during times of heightened political tension, but there have been few such incidents in the past year and it is rare for tourists, a key source of income for the kingdom to be targeted.
Officials said they were looking into motivations behind the latest blasts, which hit around after 10:00 p.m. (15:00 GMT) and killed one Thai woman selling papaya salad.
"The type of bomb is still under investigation," Hua Hin's police chief, Sitthichai Srisopacharoenrat, told AFP after the twin blasts.
"One Thai woman was killed and altogether from the two bombs 19 people were injured," said another local officer.
"Three are in serious condition and seven of the injured are foreigners: four women and three men," he told AFP, adding that the two blast sites were 50 meters (164 feet) apart.
Photos showed emergency workers evacuating victims from the area on stretchers and foreign tourists with minor cuts and injuries gathered at a local hospital.
Hua Hin is an upscale resort town about 200 kilometers (125 miles) south of Bangkok, popular with both local and foreign tourists.
It is also home to a palace for years frequented by Thailand's revered King Bhumibol Adulyadej, the world's longest reigning monarch.
The 88-year-old is currently hospitalized in Bangkok for a myriad of health complications.
The explosions hit Hua Hin ahead of a long holiday weekend in the kingdom, with many people travelling as Thais prepare to celebrate Queen Sirikit's 84th birthday on Friday.
Record tourism
Thailand's reputation as the "Land of Smiles" has suffered in recent years amid frequent road accidents, crimes against foreigners and political unrest, but tourists continue to flock to the its sandy beaches and famed temples.
The kingdom is expecting a record 32 million visitors in 2016, with the tourism industry a bright spot accounting for at least a tenth of the otherwise lackluster economy.
Thursday night's blasts come several days before the one-year anniversary of the last major attack on tourists in Thailand, a bomb in the capital that killed 20 people on August 17, mostly foreigners.
The explosive ripped through a Hindu shrine set in the heart of Bangkok that is thronged nightly by crowds of tourists and local worshippers.
Thai authorities have accused two Uighur men from western China of the bombing, which was the deadliest assault of its kind in recent years.
The two men have both denied involvement in the attack and their trial is set to begin later this month.
Thailand's military junta, which seized power in 2014 after a decade of at times deadly political unrest, has touted increased stability in the kingdom as a major accomplishment of its rule.
But the generals have been unable to quell a festering Islamic insurgency in the three most southern provinces, nearly 1,000 kilometers away from Hua Hin.
The conflict is largely contained to the far south region but has occasionally spilled into other areas.
Business conflicts have also been known to trigger small incidents of violence in Thailand.
Earlier Thursday local media reported that several people were injured by a small explosion at a market in Trang province.
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