The cabinet approved the appointment of Yuranunt "Sam" Pamornmontri as an adviser to Interior Minister Charupong Ruangsuwan at its meeting on Wednesday.
The appointment is effective from June 19.
Mr Yuranunt resigned as a Pheu Thai Party list MP to run in the June 16 by-election on Bangkok's Don Muang area, a party stronghold.
He was beaten by the Democrat candidate, the opposition party's first victory in the area in 37 years.