The ruling Pheu Thai Party has defended its casino-entertainment complex project, saying it will legalise the underground activity and allow the government to collect tax revenue from it.

According to Pheu Thai, legalising gambling and tax on the project itself could be worth more than 50% of GDP.

Casino entertainment complexes will enable the country to tap into the so-called "fun" economy worth an estimated US$13.7 trillion, the party said. 

Pheu Thai said the fun economy, which includes tourism, sports and entertainment, has been growing steadily.

The government is also pressing ahead with a bill to allow casinos to operate legally within entertainment complexes.

Individuals under the age of 20 are prohibited from entering such venues. The complexes are open to all foreigners, but Thais must pay an entrance fee of 5,000 baht.

Five venues are seen as potential hosts for this project: two in Bangkok and one each in the Eastern Economic Corridor, Chiang Mai and Phuket.