Since Suphot was found to be a repeat offender as he violated the firearms law in 2010, the court ruled that he also serve the previously suspended seven-month term.
The defence has applied for temporary release pending appellate review and posted Bt100,000 bail for both.
In their confessions, the brothers said they held a grudge against Worachet because he was pushing to amend Article 112 of the Criminal Code, known as the lese majeste law.