In its weather warning issued on Wednesday, the Thai Meteorological Department said a high-pressure system from China would cover upper Thailand and a westerly trough would prevail over the North. This would lead to summer thunderstorms on Thursday and Friday. 
People should stay safe from severe conditions, including possible flash floods, and keep away from unsecured buildings and outdoor areas. Farmers should beware of crop damage, the department said. 
From Saturday until Monday, the easterly winds will get stronger with more rain and isolated heavy downpours in Phetchaburi, Prachuap Khiri Khan, Chumphon, Surat Thani, Nakhon Si Thammarat, Phatthalung, Songkhla, Ranong, Phangnga, Phuket and Trang, the department said. 
With up to three-metre-high waves expected in the Gulf of Thailand and the Andaman Sea, all ships should proceed with caution, the department said.

Summer storms predicted for Thursday and Friday

Residents in the North, Northeast, and Central regions, including Bangkok and its vicinity, and the East are warned of summer thunderstorms with gusty winds, possible hail and isolated heavy rain on Thursday and Friday.