Christianity was introduced to Thailand by European missionaries in the 16th and 17th centuries. These early Catholic missionaries were later joined by Protestants of the Presbyterian, Baptist, and Seventh-day Adventist sects. Their converts mainly came from ethnic minorities such as the immigrant Chinese. Despite the small number of Thai converts, Christians have made several major contributions in the fields of health and education.

Thailand's first printing press was introduced by Christians, and King Mongkut (Rama IV) learned English and Latin from Christians missionaries. Though King Mongkut reportedly told one of his missionary friends "What you teach us to do is admirable, but what you teach us to believe is foolish", during his monk hood before ascending the throne, he nonetheless allowed Christian missionaries to give lectures, even in his own monastery. Christians introduced surgery, made the first smallpox vaccinations, trained the first doctors in Western medicine, and wrote the first Thai-English dictionaries.

Thailand's Christian population is estimated at 0.5% of the total population.