For what reason did Munra buy three beers for Luismi at Sarajuana's?

Anxious to be brought up to speed on the situation with Norma, mostly because of Luismi's lengthy silence around the matter, Munra takes his stepson to Sarajuana's. He then buys Luismi three beers, one after another, hoping to elicit information from Luismi as he becomes inebriated.