BAI has exempted players inside the top 15 in the BWF rankings from the trials but said shuttlers ranked between 16 to 50 in the latest world rankings.
The semifinal was a marathon affair against Indonesia's World No 5 Anthony Ginting with the Indian winning the contest 21-19, 19-21, 21-18.
Playing her second successive final in the tournament, Sindhu, a double Olympic medallist, took 49 minutes to get the better of the fourth-seeded Thai 21-16 21-8.
Former world champion Sindhu will meet unseeded Supanida Katethong of Thailand in the semifinals on Saturday
The 23rd-ranked Indian could not maintain the consistency she showed in the first game to lose 21-17, 13-21, 13-21 against her 64th-ranked opponent on Thursday night.
Also progressing was the women's doubles pair of Ashwini Ponnappa and N Sikki Reddy, who got the better of local pair Aline Muller and Jenjira Stadelmann 21-15 21-16 in straight games.
Seventh seed Kidambi Srikanth defeated Mads Christophersen in straight games in the men's singles opening round of Swiss Open badminton here on Wednesday.
The Badminton World Federation also said that many players have withdrawn from the tournament after testing positive for the dreaded virus.
The 20-year-old from Almora made back-to-back final appearances at the German Open and All England Championships in the last two weeks.