HBOT (Hyperbaric Oxygen Therapy) is a quite modern treatment in Thailand for nitrogen imbalance (decompression sickness syndrome or Caisson disease). How can we apply it to treat the autism? A hypothesis shows evidence that neurons surrounding the permanently damaged epicenter of injury can be reactivated with increased oxygen. Oxygen exists in the blood in two forms, combined with hemoglobin and dissolved in plasma. More oxygen is transported by hemoglobin, but oxygen is delivered to the tissues in dissolved form by the liquid portion of blood. HBOT can increase in plasma oxygen to the tissues including the brain. A little change in oxygen can make the better improvements in : cognitive ability, socialization, sleep, calmness, decreased stimming and language. It can make increased in Glutathione (GSH), and Glutathione (GSH) can decreased in oxidative stress with effected to remove metal compounds (mercury) to improve the autism.