Rithichai Yibcharoenporn was expelled from the Illinois State University (ISU) for misbehaviour and his "aggressive manner" towards the campus administration.

US Police said ISU staff were concerned after his April 19 enquiry about his constitutional rights to buy a gun, because the comments were made during a required writing exam and because of his previous claims of having been treated unfairly at the university.

Rithichai made his enquiry just three days after the Virginia Tech shooting by a South Korean student that left 33 people dead.

The student has the right to appeal to the US Immigration Court. If he wins he will have the right to stay in the US, but would need to find a new educational institution, said Foreign Ministry spokesman Tharit Charungvat.

"But if he chooses deportation, he will be barred from re-entering the US for 10 years," the spokesman said.

As things stand, it looks like Rithichai will be deported on May 21.

The Thai Consul General in Chicago, Narong Sasitorn, said the student had a long "negative record" at the university for his aggressive behaviour.

The university administration said the decision to expel Rithichai, who is also known as "Toro", was not connected to the Virginia tragedy.

Rather, his expulsion stemmed from a string of formal complaints dating back six months and his failure to make academic progress, said Jay Groves, a ISU spokesman.

"The timing is coincidental, because he had this record of trouble before that, and he wasn't doing anything to answer to those student codes of conduct problems," Groves said in an Illinois local newspaper Pantagraph.

"Even if the Virginia Tech incident had not happened, his problems were enough to generate his removal."

But action against the international student followed swiftly after the gun comment, the paper said.

On April 23 the university changed Rithichai's student status to "involuntary withdrawal" - an immediate dismissal without a disciplinary panel review - and the US Immigration took him into custody at the Bone Student Centre on campus.

Rithichai has a history of confrontation with the university staff. The campus filed police reports of incidents in October, November, January, March and April.

The reports focus on his arguments over exam questions, grades, his student insurance policy, student employment in the campus dining services and his later dismissal from that job. No criminal charges were filed.

Rithichai's 61-year-old mother said she was shocked about the news of her son's dismissal and allegations of misbehaviour.

"My son is not the kind of person who would slip into class with a gun," she said. "He is a person who loves to collect books, not weapons," she said, adding, "He has a lot of books."

He might have been curious about the legalities of owning a weapon in the US after the Virginia Tech shooting, said his mother, who declined to have her name published.

She admitted her son used to complain about his sour relations with the university's lecturers and staff over his academic work. "But I don't think it would be a big enough deal to expel my son," she said.

Rithichai graduated with a BA from Assumption University and earned a master's degree in language and communication from the National Institute for Development and Administration (NIDA).

His mother said he might return to resume his work as a lecturer at Silapakorn University and complete his PhD studies in Thailand.