Maj Gen Kattiya Charoenpon, an army expert, said he would appeal the verdict. Former police chief, Pol Gen Sant Sarutanond, is seeking a compensation of Bt300 million from Kattiya.
Court said Kattiya had a core in soliciting a total of 50,000 signatures to impeach Sant as allowed in the constitution in September 2004.
Kattiya, known for his outspoken, alleged that Sant involved in many corruption as well as kidnapping him.
However Court found that the defendant's statements were not accurate and tarnished Sant's reputation. Therefore, Court ruled that Kattiya paid a fine of Bt20 million with interests of 7.5 per cent.
Kattiya said he would consult with his lawyers to appeal the case.