The Administrative Court on Friday accepted Democrat Party leader Abhisit Vejjajiva's petition against Defence Minister ACM Sukumpol Suwanatat's order stripping him of his military rank.
The court also ordered ACM Sukumpol to explain his decision within 30 days.
The minister revoked the opposition leader's military rank on Nov 8 on grounds that Mr Abhisit had used fake documents to become a lecturer at Chulachomklao Royal Military Academy, a job that exempted him from the army in 1987.
The Democrat leader responded by assigning party lawyer Bandit Siriphan to file a petition against ACM Sukumpol's order on Nov 12.
The court deferred its decision on Nov 20, saying the case required further judicial review. It then asked both sides to hand in their documents six days later before holding a hearing on Friday.
The Pheu Thai Party countered by filing a petition to the Office of the Ombudsman last Sunday, asking it to investigate whether Mr Abhisit still qualifies as an MP after having his military rank stripped.
Mr Abhisit has denied claims that he used falsified military registration documents to apply for the lecturer's position.
Other Democrats earlier accused Pheu Thai of playing political games by attempting to sideline the democrat leader ahead of the recent parliamentary censure debate.