In the French Indochina war he was accused of acting as an informant for France (espionage) and was arrested for this on 12 January 1941 while at the Santa Teresa parish. But before his arrest he went to Saint Joseph's church at Ban Han on 11 January to join Father Ambrosio Kin Minlukum (its pastor) but found he was not there. He instead gathered the parishioners to remind them to attend the next Mass which he would preside over himself. He rang the bell the following morning at 8:30am which proved the trigger for the authorities to arrest him. Kitbamrung was prosecuted for "rebellion against the kingdom" and imprisoned in Bang Khwang prison. He was sentenced to over a decade of imprisonment (he would have been in prison until 1956 had he survived) where he baptized 68 prison companions and preached the Gospel to them.