This study aims to compare the youth guides' speaking scores before and after learning through English for Geotourism Instruction Innovation at Khorat Geopark Area in Nakhon Ratchasima, investigate the differences among their tasks' mean scores and their speaking components. The sample group consists of 109 youth guides who are Grade 11 English-major students from, Mueang Nakhon Ratchasima, Sung Noen and Chaloem Phrakiat Districts. The instruments include lesson plans for English for Geotourism Youth Guides, Students Manual, English Instruction Innovation for Geotourism Communication at Khorat Geopark Area Nakhon Ratchasima, and Pre-post speaking tests for English for Geotourism Youth Guides. Paired samples t-test, One-Way ANOVA, descriptive statistics including minimum, maximum, means and standard deviations are used in data analysis. Results showed that the youth guides had a significant difference between pre-and post-test scores at.00 level in English for Geotourism. They gained significantly higher post-test scores than that of the pre-test scores. A significant difference indicates that learning through English for Geotourism Instruction resulted in higher post-test tasks scores. The significant differences are also found in pre- and post-task scores and the speaking components' scores at.00 level. These findings confirm that this language innovation instruction is an effective open learning resource that can facilitate self-regulated learning and languages used in English for Geotourism. The findings can be applied to construct language innovation instruction to exclusively develop speaking skill in other English for specific purposes field.