"But he is recuperating. The original symptoms when he was first admitted were regarded as severe," said Dr Manoon Leechawengwong, who is treating the star.

Manoon said he was trying to determine how such an excessive amount of bacteria had entered the actor's circulatory system, causing a lowering of his immune system and severe muscle weakness.

"Exercise alone does not guarantee a strong immune system," he said, referring to Chatchai's exercise regime and his regular participation in sporting events.

"Rest is equally important. Sleep is vital. Everything needs to be balanced. Enough exercise, enough rest and enough food. Anyone of these done excessively is not beneficial," said Manoon.

"Like running, it could cause bones to deteriorate or some women to stop menstruating if done too much," he said.

Dr Somphon Bunnakhupt, an expert on infectious diseases at the hospital, said Chatchai's original symptoms were similar to the those suffered by singer "Big" of pop trio D2B two years ago. Somphon said the medication used to treat Chatchai was made locally, unlike that used for Big [Parawat Kittikorn] which was expensive and had to be imported.

The young singer had a road accident in which his car plunged into a polluted canal. The bacteria in the water entered his nasal passages and eventually into his brain.

Big was finally admitted to Vichaiyut Hospital, after initially being treated at a local state hospital, and received treatment from Dr Manoon.

He survived after months of treatment that cost millions of baht, but he suffered severe brain damage.

Other causes of bacteria entering the body include chronic infections, animal bites and even ordinary skin rashes.