Simon was on the court for nearly three hours before closing out a 6-7 (4-7), 7-5, 6-4 win over Lu Yen-hsun. Each player won 116 points in the match but Simon managed two more breaks in improving to 4-0 lifetime versus Lu.
He will go against Matthias Bachinger in the quarterfinals. Bachinger piled up five breaks in a 7-6 (7-5), 6-3 decision over local favorite Danai Udomchoke. Bachinger dropped just seven points on serve in the final set.
Wednesday's other second-round match was decided with two tiebreakers as Jarkko Nieminen upset No. 7-seeded Robin Haase 7-6 (7-5), 7-6 (7-4).
Tobias Kamke routed eighth-seeded Pablo Andujar 6-0, 6-1 in 56 minutes and qualifier Karol Beck topped Go Soeda 6-3, 6-7 (0-7), 7-6 (7-4) in the tournament's final first-round matches.