Do my friends need a visa to stay in Hua Hin for 3 months?

Visa Exempt Entry (without a Visa) gives an admitted to stay period of 30 days, this can be once extended with another 30 days at local Immigration. Than they have to make a border run, exit and entry other country, turn around exit and enter Thailand to get a new Visa Exempt Entry for 30 days, which can be extended again at local Immigration. Better option is to apply for a Single Entry Tourist Visa at Thai Embassy or Consulate in there home country, this gives 60 days and can be extended with 30 days at local Immigration.