After dropping the first set, Kasidit took the second and third before Medvedev, a three-time finalist in Melbourne, rallied to win 6-2, 4-6, 3-6, 6-1, 6-2, reports the Bangkok Post.
Medvedev was 3-5 behind in the third and on the brink of going two sets to one down against world No.418 Kasidit when the Russian lost his cool, slamming his racquet into the net camera repeatedly until they both became a broken mess.
Ball kids had to sweep up the debris when he lost the game and set, while the match was postponed briefly as officials ran repairs on the net.
Kasidit was broken in his opening service game as he lost the first set in just 30 minutes.
But the Thai player, who qualified for his Grand Slam debut by winning the Asia-Pacific wildcard playoff event, refused to go away.
He stunned Medvedev by breaking him at 5-4 to take the second and was well on top in the third before the Russian’s meltdown.
But Medvedev, a veteran of five setters in Melbourne, regrouped to take charge in the fourth as Kasidit began flagging and an early break in the fifth set put victory in sight for the Russian.
Kasidit, 23, was the first Thai man to compete in a Grand Slam main draw in 13 years.