The Supreme Court on Friday ruled that Prompong and Kiat-udom were guilty of libel and sentenced them to one year in jail for insulting former Constitutional Court president Wasant Soipisut.
Phongthep led other Pheu Thai Party leaders to visit the duo at the Bangkok Remand Prison.
Phonthep said he had sympathy for both, as they had been working together. He said he had not expected the Supreme Court to issue such a ruling because libel cases against most politicians have resulted in suspended jail terms.
“From now on, lawyers would have to take this ruling as a norm. If this is the case, politicians must be careful of what they say,’’ he said.
After the visit, Phongthep said both Prompong and Kiat-udom were in high spirits and were able to sleep and eat in jail.
Since the prison allows prisoners to have one visit per day, the Pheu Thai Party must arrange an appointment with families of both politicians to visit them at the same time, he said.