The question asks which pair is not correctly matched. Let`s go through each option to determine if it is correctly matched or not:
Option 1: Brazil : Reais
Brazil`s currency is indeed called Reais. So, this pair is correctly matched.
Option 2: China : Yuan
China`s currency is indeed called Yuan. So, this pair is correctly matched.
Option 3: Mexico : Pesos
Mexico`s currency is indeed called Pesos. So, this pair is correctly matched.
Option 4: Thailand : Ringgit
The currency of Thailand is not Ringgit, but Baht. Therefore, this pair is not correctly matched.
Therefore, the correct answer is option 4.
Alert - correct answer should be: 4 Thailand : Baht.