Thai authorities say all 23 victims were swept away by floodwaters and drowned. The northeast province of Sakon Nakhon was the hardest hit.
Heavy rains have brought some of the worst floods in years to Thailand's rural northeast where 23 people have died over the past month, officials said on Thursday.
Flash floods have disrupted air travel, inundated rail tracks and swallowed farmland across the rice-farming region of Isaan, affecting more than one million Thais.
Twenty-three people have died since July 5, the disaster department said in a daily update. All were swept away by floodwaters and drowned, an official said.
Junta chief Prayut Chan-O-Cha flew to the hardest-hit province of Sakon Nakhon on Wednesday to inspect a reservoir that had cracked under the downpour, triggering flash floods.
"Sonca Storm caused flooding in more than 35 provinces," he told residents, referring to a tropical storm that recently blew over from the South China Sea.
"Thai people need to understand that this area is a flood risk because we are facing global warming," added the junta chief, who joined rescue boats to hand out survival kits to stranded families.
Ten provinces are still battling severe floods as rains continue to lash the upper part of the northeast, according to the weather bureau.
In January, unseasonal monsoons deluged Thailand's south, leaving over 30 dead and wrecking infrastructure across the region.