Thailand's major commercial banks remain strong with high capital adequacy ratios, while bad loans are rising at a slower pace, the central bank said on Tuesday.

The comment came a day after the Bank of Thailand (BOT) listed the country's top five banks as "domestic systematically important banks", which warrant stricter regulation to ensure they stay secure and to reduce risks to the banking system.

An index of bank shares fell half a percent on Tuesday following the BOT's announcement the previous day, which sparked investor fears that the banks may have problems.

The five are Bangkok Bank, Krung Thai Bank, Siam Commercial Bank, Kasikornbank and Bank of Ayudhya.

But those banks are strong, with CAR ratios much higher than the BOT's requirements, Deputy Governor Ruchukorn Siriyodhin told reporters.

In 2019, the five banks must have a total CAR ratio of 11.5 percent, against the minimum requirement of 11 percent.

Bangkok Bank said its ratio was 18.7 percent as of June and KTB said its ratio was 16.27 percent.

Ruchukorn also said overall banks' non-performing loans (NPLs) were still increasing, but at a slower pace, and banks' high provisioning would be able to cope with that.

"NPLs are a lagging indicator, reflecting gradual economic growth," she said.

NPLs stood at 2.95 percent of lending at the end of June.