The flight from Bangkok to Korea is around 5-6hrs and she also has experience of DVT. According to CDC, she is considered as high risk to develop recurrrent DVT, so taking DOAC or warfarin as a prophylactic drug might be considered.
Although there are no airline restriction about recent DVT (Asiana airline and Korean air), NHS also recommened 2 wks interval from recent DVT is considered as fit-to-fly for traveller.
According to The American College of Chest Physicians published the 9th edition of their Antithrombotic Therapy and Prevention of Thrombosis Evidence-Based Clinical Practice Guidelines in February 2012. Recommendations for long-distance travelers (considered grade 2C: weak recommendation, low- or very low-quality evidence) are the following:
1. Frequent ambulation, calf muscle exercise, and sitting in an aisle seat if feasible are suggested.
2. Use of properly fitted, below-knee graduated compression stockings (GCS) providing 15–30 mm Hg of pressure at the ankle during travel is suggested. GCS appear to reduce asymptomatic DVT in travelers and are well tolerated, generally.