Line app services were down for 15 minutes on Monday due to the problem of servers in Japan, its office in Thailand said.
The most popular mobile message app in Thailand was dead, or had unstable connections for some users, from 12.45pm until it returned to normal 15 minutes later.
Line Thailand said later the problem was traced to a server in Japan.
Thais are among the biggest fans of Line, with 45 million users this year, according to a Nielsen survey.
The brief failure on Monday led to #LineCollapse being the most popular Thai-language hashtag, and some users made fun of it.
"I wondered why my girl didn't return my Line chat," one user joked.
