From this link.
NED who is the company publishing Yotsubato! Thai edition, decided to stop publish Yotsubato! because it aren’t sold well. This action made many fans angry. This is not the first manga which NED abandons. Saikano, Tenjho Tenge and others are abandoned too because the contents aren’t suitable for minor (who are the largest customers of manga in Thailand.) or they aren’t sold well.
NED is not the one who stop publish the manga which isn’t end. All major publishers in Thailand usually do it for many reason. Angelic Layer’s stop published because the publisher broke the contact. GANTZ’s reason is the same as Saikano and Tenjo Tenge. (Sex and Nude)
I’m very sad when I know this news but I can read little Japanese and Japanese edition of Yotsubato! isn’t hard to read. Only problem is it’s very expensive.