A Survey on Thai Input Methods on Smartphones <s> Other Layouts <s> We propose Conslide, a new Thai input method for compact mobile devices. To address the complexity of Thai language, our design adopts drawing approach for text input. This results in a smaller keyboard (more area for applications). With appropriate layout, users can input words without lifting finger from the screen, hence the better efficiency. Empirical result shows that the average movement distance and minimal movement time required for each Thai word are comparable to those of the quasi-Kedmanee keyboards such as Droidsans Thai keyboard. <s> BIB001 </s> A Survey on Thai Input Methods on Smartphones <s> Other Layouts <s> This paper introduces an approach to improve Thai text entry on virtual keyboards. We propose a word completion on new keyboard layouts called vowel-separated keyboard layouts. Based on a Thai writing system, all vowels locate only four positions i.e. top, bottom, left and right of a consonant. Thus, we design our keyboard layouts by grouping vowels with the same position together and place the vowel group buttons into four positions of keyboard area. This should reduce the searching time when typing vowels. While all consonants still contain in the middle area and the consonant's arrangement is based on standard Thai layout named Kedmanee layout. We design two type of the vowel-separated layouts i.e. distance-based layout and big-button layout. We compare the performance of the proposed layout with the ordinary layout. Both proposed layouts yield better performance than the ordinary one especially the big-button layout. Most of test subjects prefer to use big-button layout because the layout look more simple and they can easily find the character they want. <s> BIB002
Since the Ketmanee layout was originally designed for mechanical typewriters, many limitations of virtual keyboard (e) SwiftKey [4] (f) DroidSans Thai Keyboard  (g) Three-row Keyboard on iOS (h) Four-row Keyboard on iOS were not considered at the time of the creation of Ketmanee. A number of Thai keyboard layouts have been proposed for smartphones to improve the performance in various aspects. However, users may not be familiar with the newly-designed keyboard layouts. It may take some time for users to remember the positions of the characters and utilize the new layout effectively. Four-row Thai Keyboard on iOS was designed to make Thai characters arranged in four rows, similar to the Qwerty layout for English, as shown in Fig. 2 (h). It is done by removing a number of vowels and punctuation marks from the layout. They are grouped together and represented by one key on the layout. A user can choose those vowels and punctuation marks by pressing on the key. The keyboard will show a dialog box that allows the user to choose a character. Moreover, a number of infrequently-used letters are moved from the main layout to the shifted layout to reduce the number of buttons. Conslide is a Thai input method proposed by Sukswai and Piromsopa BIB001 . It is designed to allocate less space on the touchscreen by providing two types of buttons, i.e., presskey and slidekey. A presskey acts the same as an ordinary button as in the other virtual keyboards. A slidekey displays up to 6 characters on the button. As hinted by its name, the user can choose to input a character on the slidekey by sliding. The direction is detected by Conslide and a character is selected according to the direction. Therefore, the layout for Conslide requires only two rows of buttons as shown in Figs. 3 and 4 . Conslide has introduced a number of new ideas to improve Thai input methods. However, its performance in terms of typing speed may not be the best, compared to the others. Conslide provides a layout that is completely different from the existing Thai layout. Users may need a period of time to get used to the unique layout. Vowel-separated Thai keyboard layout is a Thai keyboard layout and input method proposed by Janpinijrut et al. BIB002 . The layout was designed based on the characteristics of the Thai writing system. Figure 5 shows a Thai phrase where the consonants are shown in gray, the vowels and punctuation marks are in black. It can be seen that the vowels and punctuation marks can appear on the left of, the right of, above, or below a consonant. The layout then arranges those vowels and punctuation marks based on their relative positions to the consonant. The consonants are arranged in the central part of the layout according to the Ketmanee layout. Figure 6 shows the layout of this virtual keyboard. Separating the consonants from the vowels and punctuation marks improves the usability and convenience of the keyboard, as all the Thai native speakers know where to find the vowels and punctuation marks. Originally, this keyboard layout was designed for people with disabilities. From their experiments, the movement of fingers required is decreased, compared to Ketmanee layout keyboards. However, users may need a short period of time to get familiar with it. Consonant-only Thai keyboard layout was proposed by Ballungpattama et al.  ,  . This layout consists of only the Thai consonants. This drastically reduces the number of keys on the layout. It results in bigger button size and more convenience for users, to select the preferred characters. However, the layout cannot be used to input new words since any vowels are not included in the layout. A technique to generate a list of candidate words has been proposed together with the layout. We will review the technique in the next section. Figure 7 shows the consonant-only Thai keyboard layout.