I believe you have to get a 90 day in Savana, then extend for a year in LOS. I know someone who did it and it was not at all easy or quick (due to Thai Immigration)
Bruce. When in the country on a visa, you have to leave then re-enter the country every 90 days(border-hop/visa-run). If you have (say) a 365 day visa (for example) and do the last visa-run on the last day of your visa term (day 364) you will be given another 90 days, thereby extending the term.