We study the WKB periods for the third order ordinary differential equation (ODE) with polynomial potential, which is obtained by the Nekrasov-Shatashvili limit of (A 2 , A N ) Argyres-Douglas theory in the Omega background. In the minimal chamber of the moduli space, we derive the Y-system and the thermodynamic Bethe ansatz (TBA) equations by using the ODE/IM correspondence. The exact WKB periods are identified with the Y-functions. Varying the moduli parameters of the potential, the wall-crossing of the TBA equations occurs. We study the process of the wall-crossing from the minimal chamber to the maximal chamber for (A 2 , A 2 ) and (A 2 , A 3 ). When the potential is a monomial type, we show the TBA equations obtained from the (A 2 , A 2 ) and (A 2 , A 3 )-type ODE lead to the D 4 and E 6 -type TBA equations respectively.