Japanese visitors and chartered flights from Japan have fully recovered after Thailand's political situation stabilised.
Tourist groups from Japan with 60-300 members each, particularly students who are normally very sensitive, have already been back to the Thai tourism market since 2012, said Anake Srishevachart, president of the Thai-Japan Tourist Association.
The move showed their confidence in Thailand, he added.
Before 2012, Japanese group tourists had shied away from Thailand for several years since the country had been hit by a tsunami in 2004, followed by the forced closure of Suvarnabhumi airport in 2008, and political violence over the past three years.
Most Japanese group tourists had shifted to Hong Kong, Malaysia and Indonesia instead.
However, he added the island row with China was also a key factor in boosting Japanese arrivals here.
The association expected Japanese tourist arrivals to continue to rise this year.
Mr Anake said an increase in the number of aviation routes to Thai cities and aggressive promotion campaigns by the Tourism Authority of Thailand in Japan last year had also helped spur demand. The Thai-Japan Tourist Association forecast Japanese visitors to Thailand will reach 1.3-1.4 million by the end of this year.
Japanese tourists rank third in numbers after Malaysians and Chinese. More than 1.2 million Japanese visited Thailand in 2012 _ a 62% increase on the previous year, while more than 210,000 Thais visited Japan in the same year.
Average spending of Japanese tourist is about 4,000 baht a day per person.
However, Mr Anake noted their travelling costs are likely to rise by 15% this year in the wake of a sharp baht gain.
According to the forecast by the University of the Thai Chamber of Commerce, the tourism industry is expected to be the main driver boosting the Thai economy in the first half of this year as exports slow.
Last year, international tourist arrivals rose by 14.4% to 22 million, leading to a 24.3% surge in tourism revenue to 965 billion baht.