From literature thymus does express ADA. From Uniprot.org, ADA is expressed in duodenum, thymus, brain placenta, b-cell lymphoma, leukemic t-cell, among other tissues. Regarding which tissues have ADA expression, here are a few articles citing expression in various tissues:
B-cell lymphoma, Pubmed ID: 6688808, 8452534
Brain, and Placenta, Pubmed ID: 15489334
Leukemic T-cell, Pubmed ID: 19690332
Thymus, Pubmed ID: 11780052