Capybaras cooled off in a pool as an intense heat wave gripped Thailand.

Footage shows the sweltering rodents soaking in a pool amid 40 degree Celsius weather at the Khao Kheow Open Zoo in Chonburi province on May 2.

The Thai Meteorological Department forecasted that eastern Thailand, including Chonburi, will experience hot weather with haze and 'very hot conditions', with temperatures possibly reaching up to 42 degrees Celsius.

Isolated thundershowers with gusty winds were also expected in lower eastern Thailand.

Capybaras are the world's largest rodents, known for their semi-aquatic nature, social behaviour, and resemblance to a giant guinea pig. They are classified under 'Least Concern' on the IUCN Red List of Threatened Species.

Thailand is baking in an extreme heat wave that has seen at least 38 die of heatstroke in the country's northeastern region since February 22.

Bangkok's heat index - or measure of apparent heat when relative humidity is taken into account - breached 52 degrees Celsius on April 30 as authorities warned locals to avoid outdoor activities.