Stephen Maguire said he didn't think Dechawat Poomjaeng was "the full shilling" after losing to him in the World Championship first round.
World number five Maguire suffered a shock 10-9 defeat to Poomjaeng.
The Thai player, ranked number 70 in the world, applauded his own shots and willed Maguire's to go awry, and spilt a bottle of water mid-frame.
"I was afraid to look in the end. Crazy things were happening. I don't think he's the full shilling," the Scot said.
"I just had to switch off. I've never seen him before but there's definitely something missing."
But he added: "He seems like a really nice boy and very genuine."
Poomjaeng came through four qualifying stages to make his Crucible debut against Maguire, beating Anthony Hamilton and Jamie Cope along the way.
The 34-year-old won the World Amateur title in 2010 and turned professional the same year, winning his first match against John Higgins. This season Poomjaeng has reached the final 32 of both the German Masters and the China Open.
The Sheffield resident, who lives with four other Thai snooker players, including former world number three James Wattana, now has a second-round date with fellow qualifier Michael White.
World number three Judd Trump said it was in snooker's interest to have players who are "good to watch".
"There are no real top-class Thai players so it's good for him to come through and hopefully that brings a bit of interest from there now," Trump said.
"I think people can relate to him. He is just a genuine person playing for his life out there. I think he was just himself and that's what the crowd like about him."
Maguire added: "The crowd seemed to take to him and got behind him at the end and he seemed to be enjoying it.
"I'll have a pint and forget about it and move on to next season."
Owen Phillips, BBC Sport's reporter at the Crucible, said: "It was box-office entertainment. But it was more Frank Spencer than John Spencer."
Poomjaeng twice took a wrong turn when entering the Crucible arena and spent much of his time throwing his arms about, twitching and fidgeting, muttering to himself, and hitting himself and the table.
In only his second season as a professional, Poomjaeng said: "I tried to relax and enjoy it, rather than be serious because that wouldn't be good for my game. It was exciting."