Prakong Chuchan, 46, a resident of Nakhon Si Thammarat’s Noppitam district, was pronounced dead at 2.35am.
A further 36 protesters were wounded in the grenade attack as they marched alongside protest leader Suthep Thuagsuban urging Bangkokians to join the Bangkok Shutdown campaign.
The grenade attack was reported about 1pm. The blast hit protesters about 100 metres from where Mr Suthep was leading the march. Initial findings found an M26 grenade was used.