Many areas will see strong wind, hail and lightning, it added.
The storms are being stirred by a high-pressure front from China, which will spread over upper Thailand and bring stronger southerly and southeasterly winds laden with moisture from the Gulf of Thailand and South China Sea, the TMD said.
People caught in thunderstorms are advised to steer clear of open spaces, large trees, weak building structures, and billboards. They are also advised not to wear or carry metal objects and avoid using mobile phones during thunderstorms.
The storm warning covers the following provinces:
Friday
North: Nan, Uttaradit, Phitsanulok, and Phetchabun
Northeast: Loei, Nong Bua Lamphu, Udon Thani, Nong Khai, Bueng Kan, Sakon Nakhon, Nakhon Phanom, Mukdahan, Chaiyaphum, Khon Kaen, Kalasin, Maha Sarakham, Roi Et, Yasothon, Amnat Charoen, Nakhon Ratchasima, Buri Ram, Surin, Si Sa Ket and Ubon Ratchathani.
Central: Nakhon Sawan, Lopburi and Saraburi
East: Prachinburi and Sa Kaew
Saturday
North: Mae Hong Son, Chiang Mai, Chiang Rai, Lamphun, Lampang, Phayao, Nan, Phrae, Uttaradit, Tak, Sukhothai, Kamphaeng Phet, Phichit, Phitsanulok, and Phetchabun
Northeast: Loei, Chaiyaphum, Khon Kaen, Maha Sarakham, Roi Et, Yasothon, Amnat Charoen, Nakhon Ratchasima, Buri Ram, Surin, Si Sa Ket and Ubon Ratchathani
Central: Nakhon Sawan, Uthai Thani, Chainat, Kanchanaburi, Ratchaburi, Suphanburi, Lopburi, Saraburi, Singburi, Ang Thong, Ayutthaya, Samut Songkhram, Samut Sakhon, Nakhon Pathom, and Bangkok and vicinity.
East: Nakhon Nayok, Prachinburi, Sa Kaew, Chachoengsao, Chonburi, Rayong, Chanthaburi and Trat
Monday
North: Mae Hong Son, Chiang Mai, Lamphun, Lampang, Tak, Sukhothai, Kamphaeng Phet and Phitsanulok
Central: Nakhon Sawan, Uthai Thani, Chainat, Kanchanaburi, Ratchaburi, Suphanburi, Singburi, Ang Thong, Samut Songkhram, Samut Sakhon, Nakhon Pathom, and Bangkok and vicinity.
South (east coast): Phetchaburi and Prachuap Khiri Khan
Easterly and southeasterly winds prevailing over the Gulf, the South and the Andaman Sea will bring more rain and possible thunderstorms to the South. Waves will rise to 1 to 2 metres in thundershowers.
Small boats in the Gulf of Thailand are cautioned to stay ashore from Sunday through Tuesday (April 30-May 2).
Weather forecast for today and tomorrow:
Bangkok and surrounding areas will experience hot weather with cloudy skies and thundershowers over 10% of the area, according to the TMD forecast.
Minimum temperatures will be 25-27C with a maximum of 34-38C and southerly winds of 10-20km/hr.
The North will have cloudy skies and high temperatures in some areas, with thundershowers and strong winds in Tak, Phitsanulok and Phetchabun provinces.
Minimum temperature of 23-26C, maximum of 38-42C.
Southerly winds 10-20 km/hr.
The Northeast will have hot weather with cloudy skies and thundershowers and strong winds in Chaiyaphum, Nakhon Ratchasima, Buri Ram, Surin and Si Sa Ket.
Minimum temperature of 23-26C, maximum of 37-39C.
Southerly winds 10-30 km/hr.
The Central region will be hot to very hot with cloudy skies.
Thundershowers in 10% of the area and strong winds, mainly in Uthai Thani, Kanchanaburi, Ratchaburi and Saraburi.
Minimum temperature 23-26C, maximum 37-40C.
Southerly winds 10-20 km/hr.
The East will see thundershowers in 20% of the area with strong winds, mainly in Nakhon Nayok, Prachinburi, Chonburi, Chanthaburi and Trat.
Minimum temperature 24-26C, maximum 33-39C.
Southeasterly winds 10-30 km/hr.
Wave height rising above 1 metre in thundershower areas.
South (east coast): Hot weather with thundershowers in 20% of the area, mostly in Surat Thani, Nakhon Si Thammarat, Songkhla, Pattani, Yala and Narathiwat.
Minimum 24-26C, maximum 34-37C.
Easterly winds 15-30 km/hr.
Wave height rising above 1 metre in thundershowers.
South (west coast): Hot weather with thundershowers in Phang Nga, Phuket, Trang and Satun provinces.
Minimum 24-27C, maximum temperature 33-37C.
Easterly winds 10-30 km/hr.
Wave height above 1 metre in thundershowers.