Synthetic approaches to flexible and adaptable thiacalix[4]arene dimer, in which the thiacalix[4]arene units constrain 1,3-alternate conformation, by molecular assembly are presented. The thiacalix[4]arene dimer shows high affinity toward Cs+ and K+ ions. Encapsulation of Cs+ by the internal cavity of the dimer strongly suggests that the size match factor drives the process. On the other hand, the K+ is encapsulated by the thiacalix[4]arenes units by supramolecular interaction (cation-pi).