Rear Admiral Winal Klom-in's mugshot has appeared widely in social media postings alongside that of a masked man in support of speculation that he is one of the anti-government protest leader's guards.
The naval officer on Saturday affirmed that he was not that man.
"I've never even met Mr Suthep," he said, adding there was no reason why he needed to take the job.
"Why would I do this? I'm a commander and an admiral. Do you really expect me to do this?"
The rear admiral said he had been a target of criticism since three of his men had been caught mingling with People's Democratic Reform Committee (PDRC) protesters.
"I just have to bear with it. That's okay. It comes with the job," he said.
Rear Adm Vinai admitted he had gone in plainclothes to several PDRC protest sites because he wanted first-hand intelligence.
He said he made similar visits during earlier rallies by the People's Alliance for Democracy (yellow shirts) in 2008 and the United Front of Democracy against Dictatorship (red shirts) in 2010.
"I just blended in. Nobody recognised me."
A Defence Ministry source said the pictures had been verfied and it had been confirmed the man was not Rear Adm Winai.